And yet, just a few days after the ABA’s poll was released, a packed Supreme Courtroom sat stunned as the five conservatives appeared entirely convinced by a legal argument that was at odds with nearly two hundred years of precedent. When four of these conservatives ultimately voted to strike the entire law down, and Chief Justice Roberts came within a hair’s breadth of giving them a fifth vote, their votes seemed like a thumb in the eye of the entire legal establishment. If we lawyers can barely predict the outcome of the most closely watched case in the country, what good are we?

A new study, however, may shine some light on what happened. The fault didn’t lie with the legal community’s lawyering skills. The culprit, rather, was the human mind itself. Specifically, the problem it has with mixing analysis with politics.

The study, by Yale Law Professor Dan Kahan and three colleagues, examines how well highly numerate individuals — people who are good at math — solve problems that lead to conclusions at odds with their political views. Kahan and his colleagues provided one of two different data sets to math-able test subjects. One data set, when analysed correctly, suggested that a gun ban increased crime. The other data set, when properly analysed, led to the opposite conclusion. What he found was that mathematically skilled individuals were far more likely to reach the correct result when that result aligned with their preexisting political views:

As Kevin Drum points out, this is the result you get when partisans are presented with a fairly simple data analysis problem that has a right and wrong answer. “If ideologues actively turn off their minds even for something this simple,” Drum writes, “there’s really no chance of changing their minds with anything even modestly more sophisticated.”

But, of course, the Supreme Court’s job is to solve analytic problems that are far less simple than the one presented in Kahan’s study. Unlike a simple math problem, constitutional law often requires judges to analyze complex questions regarding ambiguous words, uncertain historical records, conflicting interpretations, and thousands of pages of arcane judicial opinions. If a conservative partisan cannot solve a simple math problem that calls into doubt his or her view on guns, how can we expect Antonin Scalia to “solve” a much more challenging legal problem where the political stakes are much higher and the “correct” answer is much less clear cut — assuming that such an answer exists in the first place.

Of course, one rejoinder to this concern is that many conservative partisans proved quite capable of evaluating Obamacare and determining that it is constitutional. Judge Laurence Silberman, the conservative judge who warned that the challenges have no basis in the constitution, was one of two prominent conservative jurists who voted to uphold the law. The other, the brilliant but deeply conservative Judge Jeffery Sutton, has a resume that suggests he would be a sure vote for an important conservative cause, yet he defied expectations and sided with health reform. Indeed, a new, deeply researched book by libertarian law Professor Josh Blackman laying out the history of the anti-Obamacare litigation reveals that one of the architects of the lawsuit — Georgetown Law’s Randy Barnett — was initially “very pessimistic” about his case’s prospects. After reading some early op-eds attacking the law, Professor Barnett commented that “[i]f those were the best arguments that the law is unconstitutional, then I figured it must be constitutional.” So it simply is not the case that smart conservative lawyers are incapable of evaluating a case they desperately want to win and deeming it wanting.

What separates Silberman, Sutton and Barnett from the justices, however, is that they ultimately must answer to a higher authority. As Chris Mooney explains, the math problem at the center of the Kahan study was constructed to that the wrong answer appeared intuitive, while the correct answer required some calculation to determine. Thus, when a partisan in confronted with an intuitive solution to a problem that aligns with their political beliefs, they are not motivated to dig any deeper. By contrast, “more numerate people, when they sense an apparently wrong answer that offends their political sensibilities, are both motivated and equipped to dig deeper, think harder, and even start performing some calculations — which in this case would have led to a more accurate response.” In other words, the problem Kahan’s study highlights may not be that partisans lack the ability to discover counter-intuitive answers that conflict with their politics, but that they lack the motivation to do so.

Translated into judicial terms, this explains why Judge Sutton behaved so differently than Justice Scalia. A lower court judge who errs risks the shame of being overruled by a higher court, so they have a built in motivation to fully consider arguments that they may not initially be inclined to accept. Similarly, an advocate like Barnett will fare quite poorly if they cannot assess which arguments are most likely to succeed in court — even if they personally find losing arguments persuasive. Justices of the Supreme Court, by contrast, answer to no one but themselves. They lack the motivating factors that could have driven Silberman, Sutton and Barnett to look deeper than their personal prejudices.

Ultimately, however, this disparity between Sutton’s behavior and Scalia’s may indict the Supreme Court as an institution. While unaccountable judges can be trusted to decide hyper-technical questions when they have no political stake in the outcome, Kahan’s study suggests that they will replace law with politics when confronted with a contentious health care law or the scope of workers’ rights or the identity of the next president. And, indeed, the justices’ voting patterns in such politically charged cases largely corroborate this interpretation of this Kahan study.

If judges can behave, as Silberman and Sutton did in the Obamacare case, like disinterested actors unmoved by their politics, then a strong judiciary can play a very important role in maintaining a free society. But if the only thing keeping a judge honest is a more powerful judge looking over their shoulder, then it much harder to justify the massive power wielded by the Supreme Court.

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